In recent years, BPTMC is used as raw materials for the production of optical products such as optical disks, as well as synthetic resins for optical use such as polycarbonate resins for optical use. In order to supply BPTMC to this use, it is demanded to produce uncolored high purity BPTMC which is free of by-products, and besides free of high boiling point by-products or colored by-products derived from purification processes for the obtained reaction product and residual phenol or trace impurities such as sodium in high selectivity and in high yield in an industrially stable manner.
A variety of processes for the production of BPTMC are already known. According to one of such processes, phenol is reacted with TMC in the presence of an acid catalyst, and after the completion of the reaction, the resulting reaction mixture is neutralized, followed by removing water therefrom and cooling to crystallize phenol adduct crystals of BPTMC and collecting the crystals by filtration. The adduct crystals are then treated to remove phenol therefrom to provide BPTMC. In order to remove phenol from the phenol adduct crystals of BPTMC, distillation or evaporation processes are usually employed. However, these processes have a fear that the resultant BPTMC is thermally deteriorated and undesirably colored.
For instance, phenol is reacted with TMC using hydrogen chloride gas as an acid catalyst and an alkyl mercaptan as a promoter in the presence of an inactive organic solvent or in the absence of a solvent and then phenol remained unreacted is removed from the reaction mixture by steam distillation, as described in Japanese Patent Application Laid-open No. 2-88634. It is also described therein that, after the reaction, water is added to the reaction mixture, and then an alkali to neutralize the reaction mixture, followed by heating, cooling and removing an aqueous phase, thereby obtaining the desired BPTMC as residue.
A further process is known, as is described in Japanese Patent Application Laid-open No. 8-505644. According to the process, phenol is reacted with TMC using hydrogen chloride gas as a catalyst and an alkyl mercaptan such as octanethiol as a promoter. After the reaction, water is added to the reaction mixture to form a slurry, and the slurry is filtered to provide 1:1 adduct crystals of BPTMC and phenol, and then adduct crystals are broken up in warm water or in an aromatic hydrocarbon solvent such as toluene to remove phenol therefrom, thereby providing the desired BPTMC.
However, nothing has been known how to obtain high purity BPTMC in a stable manner by removing phenol advantageously from phenol adduct crystals of BPTMC.
On the other hand, in respect of 2,2-bis(4-hydroxy-phenyl)propane (referred to as “bisphenol A” hereunder), some processes for purification, in particular, those for production of high purity bisphenol A by removing phenol from phenol adduct crystals of bisphenol A are already known. For example, Japanese Patent Application Laid-open No. 4-29947 describes a process as follows. Phenol adduct crystals of bisphenol A are dissolved in a mixed solvent of phenol and an aromatic hydrocarbon and then crystallized out of the solvent to provide high purity product of bisphenol A.
A further process for production for high purity bisphenol A is also known, as is described in Japanese Patent Application Laid-open No. 5-294871. According to the process, phenol adduct crystals of bisphenol A are dissolved in water and then cooled to crystallize bisphenol A out of the water, followed by recryatallization out of an aromatic hydrocarbon solvent.
However, it is difficult to predict the behavior of production of BPTMC by a condensation reaction of TMC which is an alicyclic ketone having three methyl groups in the molecule with phenol based on the behavior of production of bisphenol A by a condensation reaction of acetone and phenol. As a matter of fact, nothing has been known how to obtain highly purified product of BPTMC which is remarkably reduced in the amount of not only residual phenol but also trace impurities of sodium, chlorine and sulfur from phenol crystals of BPTMC in high yields and in a stable manner.
The invention has been accomplished to solve such problems as involved in the known processes for the production of BPTMC by an acid condensation reaction of phenol and TMC.
Therefore, it is an object of the invention to provide a process for production of BPTMC advantageously in an industrial manner in which phenol adduct crystals of BPTMC obtained as the reaction product are crystallized from a crystallization solvent to provide highly purified product of BPTMC which is remarkably reduced in the amount of residual phenol and trace impurities of sodium, chlorine and sulfur.